Grippers with adjustable gripper pads



Dec. 24, 1968 w. KOCH ETAL I 3,417,696

GRIPPERS WITH ADJUSTABLE GRIPPER PADS FOR SHEET PRINTING Filed Dec. 13,1965 Inventors.

WER ER Koeu Ann YWQBMQ. QR u-ss BY QM; and) United States Patent 8Claims. of. 101 409 ABSTRACT OF THE DISCLOSURE A gripping device for asheet-feeding press in which a row of grippers and a corresponding rowof gripper pads coact with each other for gripping therebetween theleading edge of a sheet to be worked on in the press. The positions ofthe gripper pads are jointly or individually adjustable in a planesubstantially normal to the plane of a gripped sheet.

In sheet-fed printing presses, the sheets are gripped at their frontedges, at the pre-gripper respectively swing gripper, and also later atthe impression cylinder and at the delivery chain, by a row of gripperswhich cooperate with gripper pads. Each row forms a set of gripper padswhich is usually mounted on a common rail, which in turn is secured tothe .pregripper respectively swing grippers, to the impression cylinder,or to the delivery gripper system.

In indirect printing, as a result of the bulge formation at the contactzone between the blanket and impression cylinders, severe stressing ofthe paper occurs which leads to differences in register at the end ofthe sheet, particularly with sheets of large size and with papers of lowstrength.

It has already been proposed to compensate for these differences bydeformation of the front edge of the sheet. Such deformation is carriedout in the plane of the sheet whereby the registerof the impression isdisturbed at the front edge of the sheet. The greater accuracy ofregister achieved at the end of the sheet is obtained at the expense ofa faulty register at the front edge of the sheet.

The invention overcomes these disadvantages by means of a device whichis associated with each set of grippers to adjust the gripper pads alonga bent or curved path perpendicular to the plane of the sheet. The frontedge of the sheet is thereby effectively shortened by the consequentdeviation from a straight line. As a result the lateral edges of thesheet exert a pull on the rear edge of the sheet and cause a deformationand hence an alteration in the length of the rear edge of the sheet.This deformation takes place precisely in the same manner as at thefront edge of the sheet, in a plane substantially perpendicular to theplane of the sheet. As a result, although the required variation in theprinting width is obtained transversely to the direction of travel ofthe sheet, nevertheless no deviation from a straight line occurs in theprint.

According to the invention, in one embodiment there is provided that thegripper pads of the set are secured to a resilient rail which can bebent by means of the device. Thus a simple, robust structure isobtained. In this case, the rail may appropriately be screwed at itsmiddle within the gap of the impression cylinder for example, While itstwo ends hang freely and are each bent up or down to a certain extent bya screw. The required graduation in the bending can be achieved byappropriate reduction in the cross-section of the rail from the middletoward the two ends.

In another embodiment of the invention it is provided that a pluralityof gripper pads in a set are mounted on a common holder which can bedisplaced, by the device, out of a position in which the gripper padfaces lie parallel with the plane of the sheet, into a position in whichthe faces of the gripper pads lie in a plane which forms an acute anglewith the plane of the sheet. In this case, the arrangement is preferablysuch that the gripper pads are combined in three successive groups, ofwhich the middle group is arranged parallel with the plane of the sheet,and the two outer groups are each secured to a common holder which isadjustable in each case by a device in such a manner that they lie at anacute angle to the plane of the sheet. The adjustment of only a fewgripper pads at the ends in each case, which is sufficient in manycases, is thus obtained with very simple means.

In a further embodiment, it is provided that each gripper pad in the setis mounted for movement in a guide lying substantially perpendicular tothe plane of the sheet and is adjustable by means of the device. As aresult, the gripping surfaces of each gripper and its gripper pad remainparallel for relatively large setting distances, and the sheet is helduniformly tightly by the gripper over its whole width.

Several embodiments of the invention are illustrated diagrammatically inthe accompanying drawings which show in:

FIGURE 1 an end view of a gripper set mounted in an impression cylinderor a conveyor drum;

FIGURE 2 an end view of a gripper set in a preor swing-gripper;

FIGURE 3 a set of gripper pads on a resilient rail in a cylinder (shownin section);

FIGURE 4 a set of gripper pads on a swivelling rail in a cylinder shownin lengthwise section;

FIGURE 5 gripper pads which are mounted in individual guides and whichare adjusted by a swivelling rail in a cylinder shown in lengthwisesection;

FIGURE 6 a detail of FIGURE 4, and in FIGURE 7 a detail of FIGURE 5.

According to FIGUREI, an impression cylinder 1 of a printing press isprovided in a known manner with a plurality of grippers 3 mounted on agripper shaft 2. These grippers co-op-erate with gripper pads 4 whichare secured to a rail 5. The sheet grasped by the grippers 3 isdesignated by 6. The same arrangement, as shown in FIGURE 2, is alsousual with pre-grippcrs or swinggrippers 9 in which case the gripperpads 7 are secured to a rail 8. The grippers 9 are mounted on a grippershaft 10 which is mounted in levers 12 secured to a shaft 11. The sheetis designated by 13.

In the embodiment of the invention shown in FIGURE 3, the gripper pads14- are mounted on a resilient rail 15 which is secured to the cylinder1 by means of screws 16. By turning screws 17, the rail can be bentupwards at its ends in a plane substantially perpendicular to the planeof a sheet around the cylinder. The setting of the screws 17 is lockedby means of the lock nuts 18. The required graduation of the bending ofthe rail can be achieved by reducing the cross-section of the rail 15from the middle towards the two ends, by providing a single notch 19, ora plurality of notches 20 of different depths.

The embodiment of the invention, as shown in FIG- URE 4 shows theright-hand half of a set of gripper pads. The six middle gripper pads 21are not adjustable, supporting rail 22 being firmly screwed to thecylinder 1. However, the four outer gripper pads 23 at each end of theset are mounted on a rail 24 which can be swivelled upward about a hingepin 25 by means of a lockable screw 26 and against the downward actionof a compression spring 27 as is shown also in FIGURE 6. The grippingsurfaces of the gripper pads 23 may lie on the line such as 28 forexample. The position of the rail 24 can be locked by means of a Screw29.

In the embodiment shown in FIGURE 5, which likewise shows the right-handhalf of a set of gripper pads, and in FIGURE 7, the gripper pads 30 aremounted for movement in their axial direction by being guided in slotsin a holding rail 31 and are urged downwards by means of springs 32. Asa result, they engage an adjusting device in the form of a rail 34 whichcan be swivelled about a hinge pin 33. Pivoting of rail 34 is effectedby turning a set screw 35 while a compression spring 36 ensures contactbetween the screw 35 and a wall of the cylinder gap.

What we claim is:

1. A gripping device of a sheet-feeding press, said gripping devicecomprising in combination:

a row of grippers;

a corresponding row of gripper pads coacting with said grippers forgripping therebetween the leading edge of a sheet to be worked on in thepress;

support means for the gripper pads, said support means including aflexible rail mounting said row of gripper pads; and

adjustment means for adjusting the positions of the gripper pads in aplane substantially normal to the plane of a sheet gripped between thegrippers and the gripper pads, said adjustment means including flexingmeans for flexing said rail into a selected bent configuration in saidplane substantially normal to the sheet plane thereby correspondinglyvarying the positions of the gripper pads in reference to said sheetplane.

2. A gripping device according to claim 1 wherein said flexing meanscomprise fastening means securing said rail intermediate its ends to astationary point of support, and adjustable abutment means at each endof said rail, the position of said abutment means being selectivelyadjustable in said plane normal to the sheet plane in reference to saidstationary point of support for flexing said rail in accordance with thepositioning of the abutment means.

3. A gripping device according to claim 2, wherein said adjustableabutment means comprise set screws threaded into said rail ends andresting at one end upon a stationary support.

4. A gripping device according to claim 1 wherein the cross-sectionaloutline of said raii varies along the length thereof to impart to therail predetermined bending characteristics in response to an actuationof said flexing means.

5. A gripping device according to claim 1, wherein said rail includes atleast one notch in one of its lengthwise sides to impart to the railpredetermined bending characteristics in response to an actuation ofsaid flexing means. i

6. A gripping device of a sheet-feeding press, said gripping devicecomprising in combination:

a row of grippers; v

a corresponding row of gripper pads coacting with said grippers forgripping therebetween the leading edge of a sheet to be worked on in thepress;

support means for said row of gripper pads, said support means includinga bar having said gripper pads fixedly secured thereto and mountedpivotal in a plane substantially normal to the plane of a sheet grippedbetween the grippers and the gripper pads, between a position in whichsurfaces of the gripper pads coacting with the grippers aresubstantially Cir parallel to said plane of the sheet and a position inwhich said surfaces define an acute angle with said sheet plane; and

retaining means coacting with said bar for retaining the same in theselected pivotal position.

7. A gripping device of a sheet-feeding press, said grip-ping devicecomprising in combination:

a row of grippers;

a corresponding row of gripper pads coacting with said grippers forgripping therebetween the leading edge of a sheet to be worked on in thepress, said gripper pads being divided into three groups;

support means supporting the intermediate one of said groups inspatially fixed positions with reference to said sheet plane;

a holder for each of the outer groups; and

mounting means for each of said holders, each of said mounting meanssupporting the respective holder pivotal between a position in whichsurfaces of the gripper pads coacting with the grippers aresubstantially parallel to the plane of a sheet gripped between thegrippers and the gripper pads and a position in which said gripper padsurfaces define an acute angle with said sheet plane.

8. A gripping device of a sheet-feeding press, said gripping devicecomprising in combination:

a row of grippers;

a corresponding row of gripper pads coacting with said grippers forgripping therebetween the leading edge of a sheet to be worked on in thepress;

support means including an elongate guide member supporting at leastsome of said gripper pads, said guide member being disposed in a planeparallel to the plane of a sheet gripped between the grippers and thegripper pads, the gripper pads supported by the guide member being eachdislaceable in the same in a direction substantially normal to saidsheet plane for selectively varying the distance between said gripperpads and said sheet plane;

a common control bar disposed in engagement with the end of each of thesupported gripper pads opposite to the end facing the guide member;

pivot means pivotally supporting said control bar at one end thereof;and

adjustment means coacting with said control bar for placing the same ina selected angular position in reference to the sheet plane, saidadjustment means including spring means engaging said control bar tobias the same toward the selected angular position, and adjustablesetting means engaging said bar for retaining the same in a selectedposition against the action of said spring means thereby correspondingly varying the positions of the gripper pads in the guide member.

References Cited UNITED STATES PATENTS 1,208,731 12/1916 Blaine 101-4121,271,329 7/1918 Kyle 101-412 1,296,008 3/1919 Rich 101412 1,914,4566/1933 Parker et al 10l412 2,577,099 12/1951 Albrecht 101183 3,125,0223/1964 Reinartz et al 10l4l0 X 3,332,345 7/1967 Smyth 101409 ROBERT E.PULFREY, Primary Examiner.

J. R. FISHER, Assistant Examiner.

